The IMS bearing on Porsche M96 engines fitted to
the 996 & Boxster have gained a reputation for failure, although in
reality it does not happen to all of them. The problem is made worse
by the fact you get little or no warning that a failure is imminent
and due to the affect a failure has on the valve timing the end
result is usually catastrophic, in some cases the damage is so
server that it is uneconomical to repair. If you read the various
Porsche forums on the internet you will get a feel for the failure
rate, although it is worth bearing in mind that it is far more
likely that owners that have had problems are going to comment than
those that have had years of trouble free motoring.

Why does it fail ? Well there are many suggestions
for this, but the most credible seem to be a lubrication, poor
design and increased length of service Intervals. The bearing used
by Porsche is a sealed type bearing more commonly used in
applications outside the engine, the bearing is filled with grease
during manufacture and then sealed in with a seal either side of the
bearing, Over time with the heat generated by the engine the seals
go hard and the grease contained within the bearing seeps out but
the seals prevent engine oil getting in to lubricate it. Many have
suggested that the seal on the outer edge of the bearing should be
removed when fitted so allowing the engine oil to lubricate
the bearing The intermediate shaft has been used by Porsche
for many years, but on previous engines a plain engine bearing was
used (similar to those used for main and big end bearing) and the
bearing was lubricated by an oil supply from the oil pump, these
bearing could wear and lead to noise, but most importantly they did
not cause a catastrophic engine failure. Porsche like most vehicle
manufactures have increased the interval between services, this has
the affect of making the maintenance cost over the first three or
four years of ownership cheaper, which is particularly attractive to
leasing companies. Although oil technology has improved over the
last twenty years, the by-products of an internal combustion engine
have not! The result is that the lubrication ability of even the
most expensive oil declines over time, as the oil is degraded with
un-burnt fuel and carbon. Porsche dealers are now seeing piston and
liner damage on late 997 engines, only time will tell but perhaps
this to is caused by degrading of oil. Having spent in excess of
seventy thousand pounds on a fantastic piece of German engineering
do you really need to save a few hundred pounds by leaving the oil
in the engine for two years or twenty thousand miles. We would
suggest an oil change at least every year or better still every six
months, particularly if you are doing very short journeys, where the
engine does not get up to full running temperatures, giving the
chance for un burnt fuel to evaporate off.

So what can be done? You can't buy a replacement
bearing from Porsche, you have to replaced the whole intermediate
shaft which involves removing and completely stripping the engine. We
started to look at the possibility of sourcing a replacement
bearing, during our research we came across
LN Engineering who in conjunction with Flat 6 Innovations (both
based in the USA) have developed a repair method and parts for the
replacement of the Intermediate shaft bearing, using a stronger
ceramic bearing offering up to five times the service life of the
original bearing. Having looked at their product, method of fitment
and the large number of USA Porsche specialists using it, there
seemed little point in us reinventing the wheel! So we can now offer
their system of repair / prevention.

Over the life of the M96 and Later M97 engines,
three types of intermediate bearing have been used MY97-99 a duel
row bearing was used and can be changed without stripping the
engine, from MY02-05 a single row bearing was used, (in many ways
this bearing was a retrograde step) this bearing can also be changed
without the need to strip the engine, During the period MY99 -02 you
can find either of these bearings. From MY06-08 the bearing is
bigger and can't be removed without removing and stripping the
engine.

It is felt by
LN Engineering that the single row bearing used from MY 02-05
has a lower capacity and they feel that it should be replaced every
four years or 50,000miles, which corresponds remarkably with our
experience of IMS failure, the vast majority of the total failures
we have seen have been on this year range of vehicle, two of which
were on MY04 Boxster S one with 16,000 miles and the other with
26,000 miles, both had full service histories and were only used as
normal road cars.